Pyrotechnic devices, especially for small caliber cartridges, with mechanical percussion primers, and means for their manufacture

ABSTRACT

The device, comprises essentially, on one hand, a casing divided by a transverse wall into two spaces for receiving, one (open towards the front), the pyrotechnic useful charge of the device, and the other (open towards the rear), the explosive mechanical percussion primer for firing said pyrotechnic charge. An anvil projects from the transverse wall of the casing inside the primer housing space. At least one vent is formed in said transverse wall and connects the two said spaces. A portion of the central zone of the transverse wall of the casing is partially cut out leaving at least one portion connecting with the rest of the transverse wall and driven in towards the inside of the primer housing space so as to form an axial protuberance then constituting said anvil. The vents are formed in the central zone of the transverse wall by this driving in of the partially cutout portion of said central zone.

United States Patent [191 Finot et al.

[4 1 Oct. 14, 1975 PYROTECHNIC DEVICES, ESPECIALLY FOR SMALL CALIBER CARTRIDGES, WITH NIECHANICAL PERCUSSION PRIIVEERS, AND MEANS FOR THEIR MANUFACTURE [75] Inventors: Albert Finot; Lucien Corhin, both of Le Mans, France [73] Assignee: Etat Francais, France [22] Filed: May 21, 1973 [21] Appl. No.: 362,344

FOREIGN PATENTS OR APPLICATIONS 724 2/1883 United Kingdom 102/45 Primary ExaminerStephen C. Bentley Assistant Examiner-C. T. Jordan Attorney, Agent, or FirmLarson, Taylor and Hinds [57] ABSTRACT The device, comprises essentially, on one hand, a casing divided by a transverse wall into two spacesfor receiving, one (open towards the front), the pyrotechnic useful charge of the device, and the other (open towards the rear), the explosive mechanical percussion primer for firing said pyrotechnic charge. An anvil projects from the transverse wall of the casing inside the primer housing space. At least one vent is formed in said transverse wall and connects the two said spaces. A portion of the central zone of the transverse wall of the casing is partially cut out leaving at least one portion connecting with the rest of the transverse wall and driven in towards the inside of the primer housing space so as to form an axial protuberance then constituting said anvil. The vents are formed in the central zone of the transverse wall by this driving in of the partially cut-out portion of said central zone.

4 Claims, 13 Drawing Figures .5. Patent Oct. 14, 1975 Sheet10f2 3,911,821

U.S. Patent Oct. 14, 1975 Sheet2 of2 3,911,821

PYROTECI-INIC DEVICES, ESPECIALLY FOR SMALL CALIBER CARTRIDGES, WITH MECHANICAL PERCUSSION PRIlVIERS, AND MEANS FOR THEIR MANUFACTURE The invention relates to mechanical percussion primer firing pyrotechnic devices, of the type comprising essentially a casing divided, by a transverse wall, into two spaces intended to receive respectively, one, a useful charge of pyrotechnic nature whose composition and size are a function of the nature of the pyrotechnic device concerned and of the desired performance for said pyrotechnic device and, the other, called primer housing an explosive primer intended to be ignited by the mechanical effect of a striker and intended to ensure ignition of the abovesaid pyrotechnic useful charge.

It is convenient to indicate, at this point, that the field of application of the invention (field defined by the expression pyrotechnic devices with mechanical percussion primer) is not limited to cartridges for firearms and that it encompasses numerous other mechanically fired primer devices among which may be mentioned especially (and with the reservation that they indeed comprise a mechanical percussion primer), igniters, grenades, primer carrier tubes for artillery cartridge casings, launching cartridges for mortar shells, warheads for rockets or missiles, this enumeration having of course no limiting character.

Having given this specification, it should nonetheless be indicated that the invention has a very particular ad vantage when it is applied to cartridge munitions for war or hunting fire-arms, and especially, to cartridges of average or small caliber (caliber less than mm for example), in which case the casing which has been previously considered plays the role of a barrel for the munition and the pyrotechnic useful charge contained in the abovesaid casing that of propellant charge for the projectile of said munition (ball, shell, lead shot, grenade, etc.).

It is an object of the invention to provide means (methods and tools) for the manufacture of casings for mechanical percussion primer pyrotechnic devices of the type indicated, as well as assemblies equipped with such devices.

Before coming to the principal feature of the invention, it should be recalled that the primer proper, associated with this type of pyrotechnic device, is generally constituted by a cup containing an explosive charge and of which the bottom is oriented towards the outside so as to be strikable and deformed by the striker on firing, the abovesaid primer, generally closed by a mat, being manufactured independently of the cartridge of the device and connected and fixed in the primer housing provided in said casing.

Now, for pyrotechnic devices of this type (with a casing divided into two spaces by a transverse wall and with a primer accommodated in one of said spaces) to operate correctly, it is necessary that they include two additional elements, namely,

on one hand, at least one orifice, called a vent, arranged in the transverse wall of the casing and enabling the passage of the combustion gases of the primer towards the pyrotechnic charge of the device,

and on the other hand, a central protuberance (called an anvil) situated between the transverse wall of the device and the primer and oriented in the direction of said primer, this anvil serving as a support element on percussion of the primer of which the explosive charge is thus crushed between said anvil and the bottom of the cup of said primer, which bottom is deformed inwardly by the action of the striker.

It is important to note, on this subject, that the production of the anvil and of the vents which have been considered has hitherto posed delicate technical problems at the stage of manufacture, especially when it relates to pyrotechnic devices of which the primer carrier casing is of small caliber.

A first solution already proposed consists of constituting the anvil by a central boss forming an excess thickness of the transverse wall of the casing on the side of the housing of the primer, but the vents are then generally formed in a narrow crown at the periphery of this central boss, the piercing of such vents of small diameter (less than 1 mm for example) constituting a delicate and burdensome operation by reason of the fragility of piercing tools of small caliber necessary for this operation.

' It was then proposed, to overcome this drawback, to form a vent of relatively large diameter at the center of the transverse wall of the casing and to constitute the anvil by a distinct part, machined or stamped, connected and fixed in the container of the primer proper or in the bottoms of the casing, which solution is equally difficult.

It is a particular object of the invention to overcome the above-mentioned drawbacks, that is to say to enable, even in the case of casings of a small caliber, to produce simultaneously, at the stage of manufacture of the casing, without recourse to any additional part and without it being necessary to use fragile piercing tools of small caliber, the anvil and the one or more vents with which pyrotechnic devices of the type concerned must be equipped in order that the process of firing by mechanical percussion of their primer may develop in satisfactory and reliable manner, due to which the cost price of the device is reduced.

Another object of the invention is to reduce, all other things being equal, the weight of explosive contained in the primer, which also results in a lowering of the cost price of the device.

Yet another object of the invention is to procure a casing of the type concerned of which the vent has an increased opening on the side of the pyrotechnic charge to be ignited, which facilitates the firing of the said pyrotechnic charge.

The pyrotechnic device with mechanical percussion priming, according to the invention, comprises essentially, on one hand, a casing divided by a transverse wall into two spaces intended to receive, one (open towards the front), the useful pyrotechnic charge of the device, and, the other (open towards the rear), the mechanical percussion explosive primer intended to ensure the ignition of said pyrotechnic useful charge, on the other hand, an anvil projecting from the transverse wall of the casing on the inside of the space serving as primer housing and, on the other hand lastly, at least one vent formed in said transverse wall and causing the two abovesaid spaces to communicate, the abovesaid pyrotechnic device being characterized in that one portion of the central zone of the transverse wall of the casing is partially cut out (that is to say by leaving at least one connecting portion with the rest of the transverse wall to subsist) and turned towards the inside of the space serving as a primer housing so as to form an axial protuberance then constituting the abovesaid anvil, whilst the hole formed in the central zone of the transverse wall by this turned back portion of the partially cut out portion of said central zone constitutes the abovesaid vent, due to which there is simultaneously formed on the casing, without recourse to any special part, simultaneously, the anvil and the vent that the pyrotechnic device must comprise.

Besides, the perforated anvil thus formed by cutting out and driving in has edges with a sharp angle, which is favorable for the initiation of the primer whose sensitivity becomes increased, which enables, without alteration of the performance of the device, a reduction of the thickness of the explosive layer and, consequently, the weight of said layer. Thus for a cartridge of 5.56 mm it has been possible to reduce the explosive charge of the primer from 28 to 22 milligrams, which represents a substantial economy.

In addition, the hole (forming a vent) formed in the transverse partition of the casing has a large outlet on the side of the space containing the useful pyrotechnic charge to be fired, which obviously facilitates this firing.

It is then possible, according to a particularly advantageous solution, enabling the obtaining of an axial protuberance (forming the anvil) of maximal dimensions by driving in material oriented along the axis of the easing (that is to say in the passage direction of tools used for the manufacture of said casing), to constitute the portion of the transverse wall of the casing subjected to partial cutting out and to driving in inwardly of the primer housing, by at least one radially oriented strip, which, after cutting out and driving in, forms a sort of torque projecting into the abovesaid primer housing.

To this end, it is possible for example,

either, according to a first embodiment, to cut out a diametric strip on one of its large edges only and leave it attached by its two ends to the rest of the transverse wall, said strip, once driven in, forming inside the primer housing a sort of bridge humped in its middle zone which then constitutes a laterally opened anvil,

or again, according to a second embodiment, cut out such a diametric strip on its two large edges and on one of its small edges, thereby leaving it attached to the rest of the transverse wall by its other small side, said strip, once driven in by bending around this other small side, forming inside the primer housing a sort of central pin which plays the role of an anvil.

In all cases, the driving in of the radial orientation strip causes the appearance in the transverse wall of the casing of a large window forming a communicating vent between the primer housing and the housing of the useful pyrotechnic charge of the device.

In any case, the bottom of the casing is preferably constituted of a material (for example of metal or alloy such as steel, brass or light alloy) sufficiently ductile to lend itself in the cold to the operations of cutting out and driving in necessary for the formation of the opened anvil of the casing.

The advantage that such a casing with an opened anvil possesses has just been seen, both from the point of view of cost price of the casing and from that of the efficiency of its anvil and of its vent, and in this respect, the invention contemplates also such a casing in itself, independently of the pyrotechnic device of which it forms part (cartridge or other pyrotechnic device).

As regards lastly the means (methods and apparatus) for the manufacture of casings with opened anvils of the type indicated in the foregoing, the invention comprises a certain number of particularly advantageous features which will now be discussed more explicitly.

According to one of these features, once formed a principal chamber and a primer housing situated on both sides of a solid transverse wall of which the thickness is determined in such a way (taking into account its diameter and the constituent material of the casing), so that this wall lends itself to the simultaneous operation of cutting out and driving in before ensuring the formation of the opened anvil, this simultaneous operation is effected by subjecting the abovesaid transverse wall to the conjugate effect of a punch and of a matrix arranged axially on both sides of the transverse wall and having active facing surfaces of complementary shapes corresponding to the desired shape for the opened anvil, the abovesaid punch and matrix being actuated by a relative axial movement of closing on the active phase of the abovesaid simultaneous operation.

Preferably, this method is applied by arranging the matrix on the side of the primer housing and by making it fast to the frame of the punching machine, the punch, situated on the side of the principal chamber, being then actuated by an axial to and fro movement on each presentation of the casing. This method of proceding enables, during the manufacture in production line of the casing, the constancy of a large side to be guaranteed for the good operation of the primer, namely the distance between the top of the anvil and the rear surface of the bottom of the casing.

According to another feature, the operation of formation of the opened anvil is effected at the same time as another operation involving an outer zone of the casing and not interfering with the first operation (formation of opened anvil).

According to another feature, more particularly relating to casings comprising towards the front a collar connected to the body of the casing by a frustoconic shoulder, the operation of forming the opened anvil is effected before the operations of formation of the abovesaid collar and the abovesaid shoulder.

To illustrate the various features of the invention there will now be described, with reference to the accompanying drawings, two preferred embodiments of a casing for a cartridge according to the invention, these embodiments having no limiting character.

FIG. 1 of these drawings, shows in perspective and with parts cut out and parts removed, the bottom of a cartridge casing with mechanical percussion priming constructed according to a first embodiment of the invention,

FIGS. 2 and 3 are axial sections of this casing bottom made respectively along diametric planes IIII and III- III of FIG. 1.

FIG. 4 shows, under the same conditions as FIG. 1,

a second embodiment of the bottom of a cartridge cas-- ing according to the invention.

FIGS. 5a to Sf show the most characteristic phases of one method of manufacturing a cartridge casing such as illustrated in FIGS. 1 to 3, FIG. 5 corresponding to the phase of forming an opened anvil by a method according to the invention.

FIGS. 6a and 612 show the relative positions of a punch and of a matrix used in the said method, respecof forming the opened anvil.

tively at the beginning and at the end of the operation FIG. 7, lastly,,is an axial section of the abovesaid punch and of the abovesaid matrix,.made along the line VII--VII of FIG. 6a.

The cartridge casing 1 of which therear portion is illustrated in FIGS. 1 to 3 is a cartridge casing of small caliber, said casing beingsuitable for ball ammunition and for including for example a cartridge case of steel,

of brass or of light alloy.

The casing concerned'h as a generally conic shape and it isdivided, by atransverse wall la situated towards its base, into two distinct spaces, namely, on

one hand a principal front chamber A (open forwardly) intended to'receive the propellant charge 2 of the cartridge, and on the other hand, a rear secondary chamber B (open rearwardly) intended to serve as a primer housing for a mechanical percussion primer 3 comprising an explosive charge 3ahoused in a cup 3b fixed by being driven hard into the abovesaid primer housing B, the bottom of said cup being oriented outwardly so as to be exposed to the action of the firing pin.

According to the invention, the abovesaid casing comprises, on the side of the primer housing B, a laterally open anvil 4, in the form of a humped bridge, constituted by a diametric strip of the transverse wall 1a cut out laterally at sharp angles and driven back in the direction of the abovesaid primer housing, the abovesaid strip remaining connected to the abovesaid transverse wall through its ends.

The hole formed in the transverse wall then establishes communication between the primer housing B -and the principal chamber A, which enables (on percussion) the gases resulting from the explosion of the charge 3a of the primer 3 to reach the explosive charge 2 by passing through two lateral windows situated on both sides of the anvil 4 and through a diametric win- FIG. 1 by the fact that the casing comprises an anvil 4 constituted by a diametric strip of the transverse wall 1a cutout laterally with sharp angles and at one of its ends and curved at right angles towards the primer housing B, the abovesaid strip remaining connected to the abovesaid transverse wall through its other small side.

There will now be described, with reference to FIGS.

5a to 7, a method of manufacturing by stamping and drawing a cartridge case of the type contemplated by the invention, this process bringing into play a method according to certain features of the invention for the formation of the opened anvil of the abovesaid casing.

FIGS. 5a to 5] show a certain number of successive stages, particularly characteristic, of this process of manufacture.

Starting from a solid washer (FIG. 5a), for example of brass, steel or light alloy, this washer is subjected to stamping ensuring the formation of a cup with a cylindrical lateral wall (FIG. 5b) which is then subjected to a series of drawing steps (of which one is illustrated in FIG. 50) if necessary separated by heat treatments.

Once the last drawing/has been effected (or at the time of the latter), a stamping of the bottom of the casing is effected, so that the latter has, at this stage of the process of manufacture and as shown in FIG. 5d, a principal chamber Aand a primer housing B separated by a transverse wall la in which there must then be formed an opened anvil projecting into said primer housing B.

According to the invention and as illustrated in FIG. 5e, the simultaneous formation of the anvil 4 and of the corresponding vents is ensured by subjecting the transverse wall 1a to the conjugate effect of a punch 5 and of a matrix 6 arranged axially on both sides of the transverse wall la, the matrix 6 being preferably situated on the side of the primer housing B and rendered fast to the frame 7 of the punching machine, whilst the punch 5 is situated on the side of the principal chamber A and mounted so as to be capable of being positioned close to the abovesaid matrix by an axial sliding movement shown by the arrow F in FIG. 6b.

There is shown in FIG. 6a, the punch 5 and the matrix 6 just before the cutting out of the wall la, and in FIG. 6b, these two elements once the opened anvil 4 has been formed, the active portions of the abovesaid punch 5 and matrix 6 having, FIGS. 6a, 6b and 7, complementary shapes as a humped bridge corresponding to the embodiment of the anvil illustrated in FIGS. 1 to 3.

This operation of formation of the opened anvil can be accomplished at the same time as an operation of forming a beading of the outer base 8 by means of a special tool.

When the production of the casing 1 includes an operation of forming a collar and a shoulder (see FIG. 5]), the method according to the invention, for the formation of the opened anvil 4, must then come into play before the abovesaid operation of formation of the collar and of the shoulder, so that the restriction constituted by the collar does not prevent a punch of sufficiently large diameter from engaging in the principal chamber A.

We claim:

1. A casing for a mechanical percussion primer pyrotechnic device, comprising a casing body including a transverse wall which divides the casing body into a first, forward opening chamber adapted to house a pyrotechnic charge and a second, rearwardly opening chamber adapted to house an explosive mechanical percussion primer for firing the pyrotechnic charge, said transverse wall including a central part which is partially cut from the remainder of the transverse wall and forced rearwardly with respect thereto so as to project into said second, rearwardly opening chamber, saidtransverse wall including slits therein which separate said central part from the remainder of the wall along at least two edges of the central part while leaving at least one portion of the central part which is connected to the remainder of the wall, a portion of the central part being separated from the remainder of said wall an amount sufficient to define an opening between a portion of at least one of said edges of said central part and the portion of the remainder of the wall which originally bordered that edge, said projecting central part constituting an anvil and said opening constituting a vent between said first and second chambers.

2. A casing as claimed in claim 1 wherein said central part comprises a diametrical strip formed by first and second spaced diametrical slits in said transverse wall, said strip being joined to the transverse wall at the ends thereof, a central portion of said strip constituting an anvil and projecting into said second chamber to define first and second said vents between the lateral edges of said strip and the remainder of the transverse wall.

3. A casing as claimed in claim 1 wherein said central part comprises a strip cut out from the remainder of said wall on three sides, a first, free end of said strip projecting into said second chamber and the other end being joined to the remainder of said wall, the free end of said strip constituting said anvil and the space left in the remainder of said wall by said projecting free end constituting said vent.

4. Mechanical percussion primer pyrotechnic device including a pyrotechnic useful charge and an explosive mechanical percussion primer, comprising essentially, on one hand, a casing divided by a transverse wall into two spaces, one said space, open towards the front, being for housing the pyrotechnic useful charge of the device, and the other said space, open towards the rear, being for housing the explosive mechanical percussion primer for firing said pyrotechnic charge, on the other hand, an anvil projecting from the transverse wall of the casing inside the space serving for the housing of the primer, and lastly on the other hand, at least one vent formed in said transverse wall and connecting the two said spaces, said pyrotechnic device comprising a portion of the central zone of the transverse wall of the casing partially cut out so as to leave at least one portion connecting with the rest of the transverse wall, and driven in towards the inside of the space serving as said primer housing so as to form an axial protuberance then constituting said anvil, said vent being formed in the central zone of the transverse wall by said driving in of the partially cut-out portion of said central zone, said portion of the transverse wall of the casing which is partially cut-out and driven in being constituted by at least one radially oriented diametric strip which, after said cutting out and driving in, constitutes a sort of tongue projecting into said primer housing, said strip comprising a diametric strip which is cut out on one of its small sides and attached to the rest of the transverse wall by its other small side so as to form a hinge, said diametric strip, once driven in by bending around said other small side, forming inside the primer housing a sort of central eye of which the free end of the strip plays the role of an anvil. 

1. A casing for a mechanical percussion primer pyrotechnic device, comprising a casing body including a transverse wall which divides the casing body into a first, forward opening chamber adapted to house a pyrotechnic charge and a second, rearwardly opening chamber adapted to house an explosive mechanical percussion primer for firing the pyrotechnic charge, said transverse wall including a central part which is partially cut from the remainder of the transverse wall and forced rearwardly with respect thereto so as to project into said second, rearwardly opening chamber, said transverse wall including slits therein which separate said central part from the remainder of the wall along at least two edges of the central part while leaving at least one portion of the central part which is connected to the remainder of the wall, a portion of the central part being separated from the remainder of said wall an amount sufficient to define an opening between a portion of at least one of said edges of said central part and the portion of the remainder of the wall which originally bordered that edge, said projecting central part constituting an anvil and said opening constituting a vent between said first and second chambers.
 2. A casing as claimed in claim 1 wherein said central part comprises a diametrical strip formed by first and second spaced diametrical slits in said transverse wall, said strip being joined to the transverse wall at the ends thereof, a central portion of said strip constituting an anvil and projecting into said second chamber to define first and second said vents between the lateral edges of said strip and the remainder of the transverse wall.
 3. A casing as claimed in claim 1 wherein said central part comprises a strip cut out from the remainder of said wall on three sides, a first, free end of said strip projecting into said second chamber and the other end being joined to the remainder of said wall, the free end of said strip constituting said anvil and the space left in the remainder of said wall by said projecting free end constituting said vent.
 4. Mechanical percussion primer pyrotechnic device including a pyrotechnic useful charge and an explosive mechanical percussion primer, comprising essentially, on one hand, a casing divided by a transverse wall into two spaces, one said space, open towards the front, being for housing the pyrotechnic useful charge of the device, and the other said space, open towards the rear, being for housing the explosive mechanical percussion primer for firing said pyrotechnic charge, on the other hand, an anvil projecting from the transverse wall of the casing inside the space serving for the housing of the primer, and lastly on the other hand, at least one vent formed in said transverse wall and connecting the two said spaces, said pyrotechnic device comprising a portion of the central zone of the transverse wall of the casing partially cut out so as to leave at least one portion connecting with the rest of the transverse wall, and driven in towards the inside of the space serving as said primer housing so as to form an axial protuberance then constituting said anvil, said vent being forMed in the central zone of the transverse wall by said driving in of the partially cut-out portion of said central zone, said portion of the transverse wall of the casing which is partially cut-out and driven in being constituted by at least one radially oriented diametric strip which, after said cutting out and driving in, constitutes a sort of tongue projecting into said primer housing, said strip comprising a diametric strip which is cut out on one of its small sides and attached to the rest of the transverse wall by its other small side so as to form a hinge, said diametric strip, once driven in by bending around said other small side, forming inside the primer housing a sort of central eye of which the free end of the strip plays the role of an anvil. 